Ultrasensitive fluorescence immunoassay of pepsinogen I based on enzyme-triggered decomposition of AuNCs/MnO 2 .

Gastric cancer is a prevalent malignant tumor of the gastrointestinal tract accompanied by a high mortality rate; therefore, early gastric cancer screening is critical for improving patient survival. In this study, we present a facile fluorescence immunoassay for highly sensitive screening of pepsinogen I (PG I) based on a one-pot biomimetic mineralization process for the synthesis of gold nanocluster-anchored manganese dioxide (AuNCs/MnO 2 ) nanosheets. MnO 2 first quenches the fluorescence of AuNCs through the Förster resonance energy transfer effect, whereas the introduction of ascorbic acid (AA) leads to the decomposition of MnO 2 and rapidly recovers the fluorescence of AuNCs. Based on the above principles and phenomena, we developed a sensitive fluorescence immunoassay for the in situ generation of AA to detect PG I. Specifically, in the presence of PG I, the sandwich-type immunoreactivity-enriched alkaline phosphatase-labeled secondary antibody catalyzes the production of AA from the substrate, which enhances the fluorescence intensity. Under optimized conditions, the fluorescence intensity increased linearly with the concentration of PG I (0.05 to 200 ng mL -1 ) with a limit of detection (LOD) of 0.013 ng mL -1 (S/N = 3). The designed sensing platform has good stability (more than one year) and excellent anti-interference capability and demonstrates satisfactory accuracy for detection in real samples compared to commercial ELISA kits.